GB2547704A

GB2547704A - Method to determine the intake air temperature in an engine system

Info

Publication number: GB2547704A
Application number: GB1603442.3A
Authority: GB
Inventors: Aggoune Karim; Randazzo Stephane; Muller Martin
Original assignee: Delphi Automotive Systems Luxembourg SA
Current assignee: BorgWarner Luxembourg Automotive Systems SA
Priority date: 2016-02-29
Filing date: 2016-02-29
Publication date: 2017-08-30
Anticipated expiration: 2036-02-29
Also published as: GB201603442D0; GB2547704B

Abstract

Disclosed is a method of estimating the intake air temperature in a turbocharged internal combustion engine 1 at a point upstream of the turbocharger compressor 6. The method comprises measuring the boost air temperature at a point downstream of the compressor 6 of the turbocharger 5, estimating the effect of the turbocharger compressor 6 on the temperature of the air passing through it and then determining the intake air temperature based on the measured boost air temperature and the effect of the turbocharger compressor 6 on the air. The arrangement means that an air temperature sensor in the air intake is not necessary. The method may also take account of vehicle speed, ambient temperature and make adjustments for exhaust gas recirculation and air coolers.

Description

Method to determine the Intake Air Temperature in an Engine System Field of the Invention

The invention relates to determining intake temperature and has application particularly to turbocharged engine systems.

Background to the Invention

It is preferable for the control of turbocharged engines to have intake air temperature information. Most turbocharged engines currently use an intake air temperature sensor. However this adds component and assembly costs. It is an object of the invention to provide air intake temperature without the use of a sensor therefor.

Statement of the Invention

In a first aspect is provided a method of estimating the air intake temperature in a turbocharged engine at a point upstream of the turbocharger comprising a) measuring the boost temperature at a point downstream of the compressor of the turbocharger and the engine inlet manifold; b) estimating effect of the turbocharger compressor on the temperature passing through it; c) determining the air intake temperature based on the measured boost temperature at a) and the effect determined from step b).

Step b) may include the step d) of determining the degree to which the compressor is operational.

Step d) may be performed by determining if the increase/decrease is above a threshold rate.

The method may include measuring the external/ ambient temperature and the determined air intake temperature based on this parameter additionally.

The method may include additionally determining the air flow rate passing thought the air intake and/or vehicle speed and using one or both of these parameters additionally in step c).

The method may include determining a cooling factor, and adjusting the determined air intake temperature computed at step c) using the cooling factor, where said cooling factor is determined from one or more of the following parameters; vehicle speed, manifold temperature; external temperature and air flow throught the intake.

Said engine system may also include an intercooler located between the engine and the compressor and the method includes determining the cooing factor based on the difference between a measured value of the temperature between the intercooler and engine and either the measured boost temperature, estimated air intake temperature from step c), or a measured ambient temperature.

The cooling factor may be based on said difference and the engine speed, and using said factor in step c)

Said cooling factor may be computed /adjusted by a further factor, said further factor being dependent on air flow and/or vehicle speed.

Brief Description of Drawings

The invention will now be escribed by way of examples and with reference to the following figures of which:

Figure 1 shows a schematic diagram of a turbo-charged engine;

Figure 2 shows a schematic figure of an engine system including an intercooler; and,

Figures 3 a to e are schematic diagrams showing functional blocks of methods according to various examples.

Detailed Description of the Invention A turbocharged engine requires the intake air temperature information to compute various parameters such as compressor intake flow, compressor speed estimation, intake air specific heat, compensation and such like and in prior art systems the use of a dedicated sensor provides this data.

The inventors have considered estimating the air intake temperature based i.e. imputed on temperatures established at other locations in the engine system, such as upstream throttle temperature sensor, ambient temperature sensor; however use of an imputed temperature often leads inevitably to a boost control error. The lower the error is, better accurate is the boost control.

Figure 1 shows a schematic diagram of a turbo-charged engine 1 including a main engine block 2 having an air inlet flow path 3 and exhaust flow path 4. A turbocharger 5 is located as shown, including a compressor 6. Supply of air to the cylinders is via an intake manifold 8. A throttle 7 is shown. The manifold air temperature is that temperature of air in the manifold and the boost air temperature is the temperature defined as between the compressor and the manifold e.g. upstream of the throttle. The air intake temperature is defined as the temperature of the air entering the compressor.

In one aspect a dedicated system and method of determining air intake temperature is provided. In a simple embodiment the intake air temperature is estimated/computed based on the boost temperature which is measured by a boost temperature sensor already present, and adjusted according to the operation of the turbocharger. So in other words, the estimate of the air intake temperature can be based solely or mainly on the (saturated) boost temperature for which sensor(s) are usually provided for this parameter. By a smart technique, in examples, the effect of the compressor of a turbocharger is taken into account. Generally speaking where there is no compression, the (measured) boost temperature is generally equal to the air intake temperature. Operation of the compressor will have a compressive effect on the air from intake to boost (post compressor) and will consequently affect the boost temperature in relation to the air intake temperature. In a smart technique developed by the inventors, operation of the compressor (turbo) can be determined from characteristics of the boost temperature alone; in other words no other data are needed (such as turbo speed). If the measured boost temperature increases at a high rate (e.g. above a threshold) then it is assumed in one example that the compressor (turbo) is operational. If this is the case the air intake temperature can be estimated from the boost temperature, and empirical data or calibration (based on operation of the turbocharger). Thus a 2-D table or look-up map may be used to determine air intake temperature from boost temperature and whether the turbo is operating. So in summary, the air intake temperature is also computed (e.g. adjusted) based on compressor effects e.g. to saturate it when the compressor increases the inlet air pressure.

In refined methods, the air intake temperature is also computed based on either i) effects (such as cooling) due to the vehicle speed and/or ii) the ambient i.e. external temperature. In such methods a raw value for the air intake temperature is computed as described (from the measured boost temperature and turbo/compressor effects). The air intake temperature is then further computed (e.g. adjusted) based the effects (such as cooling) of vehicle speed and /or ambient temperature.

According to one refined example the following inputs are used to estimate the air intake temperature: a) upstream throttle temperature b) ambient air temperature (external) c) intake manifold air temperature d) vehicle speed e) intake air flow.

Further, in refinements, the methodology as mentioned also takes into account the cooling effect; i.e. the difference between the saturated boost temperature and the manifold air temperature . Here the cooling effect from the boost temperature sensor to the manifold backward to the intake air temperature is determined and used to adjust the (intake air temperature) IAT. The cooling effect can be determined from experimentation, observation or historic data and may be implemented in the methodology by calibration charts or look-up tables. If the engine has an intercooler water pump, this may be calibrated before.

The value of air intake temperature is also dependent on ambient air temperature which may be provided by a sensor already present e.g. that which is also displayed to the driver of modem vehicle systems. So the estimation or calculation of IAT may also be dependent (i.e. adjusted) dependent on this parameter; in examples the ambient (or external) temperature may be used with an off-set (simple ID look up table) to adjust a initially computed (or raw) value of IAT.

The air intake temperature may also depend on the speed dependency, i.e. the speed of the vehicle fitted with the engine is travelling. In examples the vehicle speed may be filtered to provide a number of discrete speed values or categories. In an example, this filtered vehicle speed is used to differentiate three filter coefficients: one for low, intermediate and high vehicle speeds. This filter coefficient is then used to calculate the final intake air temperature. The filter vehicle speed, combined with the air flow, is also used to leverage the cooling effect in the raw IAT calculation. Indeed, depending on the vehicle speed and the air flow, the cooling effect varies.

In one example a raw value of IAT is determined by the addition of the saturated boost temperature, the offset temperature based on external air temperature and the leveraged cooling effect. In a refined example the IAT may be more accurately determined by applying a low pass filter based on raw IAT.

In a refined example the cooling effect is determined in systems which include an intercooler. Figure 2 shows a schematic figure of an engine system comprising an air filter 11 upstream of a compressor of a turbo 12. The air intake temperature to be determined is that at location 16. Air from the compressor may pass through an optional intercooler 13 before entering the engine cylinders 4. The variable of the temperature of the air between 12 and 13 is the boost temperature 17 which is optionally measured and typically the temperature between the intercooler and manifold is measured at 18. The airflow throught he system may be optionally measured at any point e g. at location 19.

Figure 3 shows schematic figures of functional/processing blocks used according to examples where some or all of the above effects are taken into account. So in this example as described above the determination of IAT is based on up to five (estimator) inputs: boost (upstream throttle) temperature [°K] (varl), manifold temperature [°K] (var2), external temperature [°K] (var3), vehicle speed [km/h] (var4) and mass airflow [g/s] (var 5).

Examples A i)

Figure 3a shows a basic example. In the first estimator block A, the input parameter is the measured boost temperature (var 1) from a boost temperature sensor, measured by a sensor at the location (17), downstream of the compressor (12) upstream the intercooler (13) see figure 2. This parameter is used to determine a value for the Intake Air Temperature - this can also be regarded as a raw value which is later refined, and can be referred to as the saturated boost temperature (var 6).

In sub-block A1 and A2 any effects of the turbo are computed. In block A1 is decided that there is no saturation (effect of the turbo) and the raw air intake temperature or var 6, is assumed to be the is the boost temperature as measured by the sensor. So in other words temperature, varl is used as var 6, when the compressor does not create additional air pressure/effect in the inlet duct.

When the compressor pressurizes the air, this will have an effect on var 6, the imputed air intake temperature. It could be regarded, that varl is considered is “saturated” in this case. This is determined in one example if the measured boost temp of var 1 increases at a rate above a threshold for example. If so then in block A2 the var 6 is based on the boost temperature var 1 but adjusted by adding/subtracting by an increment or multiplying by a factor. Such an increment or factor can be determine empirically or calibration/experimentation. It is to be noted that although we are speaking here about compressor having an effect on the air measured after the compressor (boost), this effect is used to go from the air temperature measured downstream of the compressor (boost) to estimate temperature at the intake i.e. upstream of the compressor.

In an example the effect of the compressor on the estimation of air intake temperature is implemented according to the figure as follows; the last measured value of varl is “frozen” and incremented by offset (this time-based and can be calibrated) - this occurs in functional sub-block A2. The transition from (Al) to (A2) is triggered by the following equation: (varl)n-(varl)n.i > Threshold. The transition from (A2) to (Al) is triggered by: time out of a timer initialized once (A2) is active or (var6) > (varl).

In block F the variable var 6 the rough estimate of air intake temperature is may be optionally input to a lag/lead filter to determine the actual real time temperature. ii)

In a refined example the effects of ambient temperature are determined and the raw value of IAT is adjusted accordingly . Here optional functional block E determines an adjusting factor such as a base offset (var 8). The input to block E is external (ambient temperature) var3 which is input to a ID lookup table (see block El). The output of this ID lookup table may be then filtered (block E2) to calculate var8 which is the base offset. Var 9 is the air intake temperature estimated.

Example B i) Figure 3b shows a refined example. In this example the process steps as in Example A are carried out.

In addition the model/method is refined by adjusting the estimated IAT based on a cooling effect.

Where a vehicle has e.g. an intercooler located between the compressor and the engine inlet (e.g. manifold); the intercooler acts as a heat sink taking heat from the air passing (intake) though it and transmitting it to the atmosphere or engine space. Alternatively the intercooler, if at a higher temperature than the external (ambient engine compartment temperatures) it will impart heat to the air passing though it. Typically also there is a temperature sensor located between the intercooler and engine; generally therefore a manifold temperature sensor is already provided. Thus the temperature differential across the intercooler along with airflow (ie/e, mass or volume flow rate through intake) and/or vehicle speed will provide information on the temperature e.g. in the engine compartment..

Figure 3b shows a generic block B which has an input from var 6 (which could be considered as var 1 under certain conditions as explained above or var 1 optionally used alternatively) as well as an input from either an external temperature sensor and/or the manifold temperature sensor. Dependent on these temperatures and the value of air flow and/or engine speed a cooling effect or factor var 7 is determined used to adjust the value of the var 6 which is raw value of air intake temp. Var 7 is fed to block F.

Optionally an input from the external temperature sensor from block E is fed to block B.

In an embodiment a temperature delta or difference across the intercooler is determined or estimated. This can be done by performing the operation of determining the difference between (var 2 and var 1/6) or (var 2 and var 3). This difference can be used in a two or three dimensional look up table or map along with air flow through the intake and optionally vehicle speed. This gives an indication of heat dissipated or drawn in via the intercooler. This differential is used along with air flow and optionally vehicle speed to determine the adjustment (var 7).

It is to be noted that in this example the functionality of block E may omitted; in other words it is optional. ii)

Figure 3c shows a refined example. This shows more details of one method of block B above. The figure is similar to figure 3b and the operational steps are the same except the functional block B is shown in more detail. Block B is used to determine a cooling effect factor (var 10) which is input to block C. An input to the sub-block B1 is the measured manifold temp (from a sensor) referred to as var 2. As an alternative the value var 3 can be used. To establish a first approximated dependency of the cooling effect (var 10), a first temperature delta is created: the difference between varl/var 3 and var 6 as before.

The difference between the boost temperature (saturated) var 1 or var 6 and the measured manifold temperature - see block Bl. So var 10 = (var 6-var 2). If the turbo is operating then this var 10 may be amended i.e. depending if the boost temperature is considered saturated or not; i.e. the same conditions of as explained above with reference to var 6 and block A. If the boost temperature is considered not to be saturated the cooling effect var 10 is set at a cooling effect raw value. To recap this delta is used because var 2 may be cooled down by the intercooler, which acts as a heat sink the external air. This is a quiet rough estimation, but sufficient to determine a cooling factor which is in fact a “delta temperature”. So block B2 is used to determine var 10 if the conditions of block A2 are current otherwise the block Bl is used to determine varlQ is conditions of block Bl are present. Based on this and the input of vehicle speed and or mass flow (var Alvar 5) the cooling effect is input to block F to adjust the raw value of IAT (var 6). hi)

Figure 3d shows a refined example where var 10 is input to block C which may comprise a look-up table or map to determine an adjustment var 7, based on the input of vehicle speed var 4. It is to be noted that block B and C of figure 3d can be considered equivalent to block B of figure 3c. So to recap figure 3d shows a refinement of how block C works. In block C the (raw) cooling factor (var 10) and optionally vehicle speed are the inputs of a two dimensional lookup table (Cl), used to provide a vehicle speed dependent cooling factor (var 11).

Example C

Figure 3e shows a yet further refinement where an additionally block D determines a factor to be applied to var 11 dependent on air flow and/or vehicle speed. So in block D there are two inputs air flow and vehicle speed. These are used to determine a factor equal to (1, -1 or 0) which is then applied to the speed dependent cooling factor (var 11) by multiplying by the factor that can be either. The selection of 1, -1, or 0 made via a truth table that can be summarized as follows: when the vehicle speed and the airflow are simultaneously lower than respective thresholds, the factor is 1 (corresponding to a “heating effect”) On the other hand, when the vehicle speed and the airflow are simultaneously higher than respective thresholds (different from those mentioned before), the factor is -1 (corresponding to a “cooling effect”). Any other conditions lead to a factor equal to 0, meaning that no cooling (or heating) effect is considered (see section Dl). Off course the skilled person would understand that more refined methods can be used such as (e.g. 3 dimensional) look up tables can be used to determine a factor (var 12) output from block D (or dependent on both air-flow and/or vehicle speed) which is used to amend the refined cooling affect (var 11). Functional block D is optional; e.g. where air flow data is not obtainable functional block D is omitted.

Of course the skilled person would consider alternatives. In a general embodiments the factor applied at box X may be any function of air flow and/or vehicle speed, and can be provided by a two or three dimensional look up table.

General

As mentioned in functional block F the IAT is determined. The inputs to block F are var 6 optionally var 7 and var 8. The var 6 is the saturated boost temperature which is the main factor used to determine/estimate the IAT. The IAT may be assumed to be var 6 in a simple example.

In refined examples the IAT is dependent on the var 6 with either var 7 (cooling offset) and/or var 8. So where all the values are used to determine IAT, the three variables at sub-block FI are used (e.g. summed) to determine a value which then may be filtered. In the example, the unfiltered value of var9 is preferably realigned via an additive term (var8) depending on the external temperature (var3). The intake air temperature (var9)) is the results of an addition (FI) and then a filtering (F2).

In refinements, the functional blocks B with optionally C and D, are used to determine a cooling offset (var7) or factor which is used along with var 6 to provide the estimated intake air temperature (var9) . Thus again these blocks therefor effectively provide an amendment/adjustment (var7) to the raw value of var 6 calculated above, and this is he based on external conditions such as vehicle speed (var4) and/or airflow (var5) as well as the temperature differential across the intercooler. In other words the raw value of estimated air intake temp (var 6) is adjusted for such effects

Claims

1. A method of estimating the air intake temperature in a turbocharged engine at a point upstream of the turbocharger comprising a) measuring the boost temperature at a point downstream of the compressor of the turbocharger and the engine inlet manifold; b) estimating effect of the turbocharger compressor on the temperature passing through it; c) determining the air intake temperature based on the measured boost temperature at a) and the effect determined from step b).

2. A method as claimed in claim 1 where step b) includes the step d) of determining the degree to which the compressor is operational.

3. A method as claimed in claim 2 where step d) is performed by determining if the increase/decrease is above a threshold rate.

4. A method as claimed in claim 1 including measuring the external/ ambient temperature and the determined air intake temperature based on this parameter additionally.

5. A method as claimed in any previous claim including additionally determining the air flow rate passing thought the air intake and/or vehicle speed and using one or both of these parameters additionally in step c).

6. A method as claimed in any previous claim including determining a cooling factor, and adjusting the determined air intake temperature computed at step c) using the cooling factor, where said cooling factor is determined from one or more of the following parameters; vehicle speed, manifold temperature; external temperature and air flow throught the intake

7. A method as claimed in claim 6 where said engine system includes an intercooler located between the engine and the compressor and the method includes determining the cooing factor based on the difference between a measured value of the temperature between the intercooler and engine and either the measured boost temperature, estimated air intake temperature from step c), or a measured ambient temperature.

8. A method as claimed in claim 7 where the cooling factor is based on said difference and the engine speed, and using said factor in step c).

9. A method as claimed in claim 8 where said cooling factor computed adjusted by a further factor, said further factor being dependent on air flow and/or vehicle speed.