CN108564172A - Organic Rankine Cycle output power predicting method based on BP neural network - Google Patents

Organic Rankine Cycle output power predicting method based on BP neural network Download PDF

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CN108564172A
CN108564172A CN201810361923.8A CN201810361923A CN108564172A CN 108564172 A CN108564172 A CN 108564172A CN 201810361923 A CN201810361923 A CN 201810361923A CN 108564172 A CN108564172 A CN 108564172A
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neural network
data
output power
rankine cycle
organic rankine
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杨富斌
张红光
侯孝臣
田亚明
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Beijing University of Technology
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Beijing University of Technology
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    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06NCOMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
    • G06N3/00Computing arrangements based on biological models
    • G06N3/02Neural networks
    • G06N3/08Learning methods
    • G06N3/084Backpropagation, e.g. using gradient descent

Abstract

Organic Rankine Cycle output power predicting method based on BP neural network, belongs to Thermal Power Engineering Field.Include the following steps:The acquisition of multigroup Organic Rankine Cycle operation data, every group includes following parameter:Volume flow, expanding machine torque, expander inlet pressure, outlet pressure of expansion machine, expander inlet temperature, condensator outlet temperature, working medium pump discharge pressure and the expanding machine output power of organic working medium;The normalized of gathered data;The foundation of BP neural network;The training and test of neural network;The anti-normalization processing of neural network output data, that is, expanding machine output power in test data.Compared with traditional thermodynamics analysis methods, the neural network model that the present invention is built can fast and accurately predict Organic Rankine Cycle output power, avoid the operation mechanism research to various parts, and it can be obviously improved working efficiency and precision of prediction, reliable guide is provided for the optimization of Organic Rankine Cycle.

Description

Organic Rankine Cycle output power predicting method based on BP neural network
Technical field
The present invention relates to a kind of Organic Rankine Cycle output power predicting method based on BP neural network, belongs to thermal energy work Journey field.
Background technology
During China industrializes fast-developing, there is a large amount of waste heat energies, such as:Fume afterheat, cooling medium Waste heat, waste vapour waste water residual heat, high-temperature product and afterheat of slags, chemical reaction heat and combustible exhaust gas and waste material waste heat etc., in addition to Can by technological transformation upgrade realize to these waste heat energies it is efficient utilization except, heat recovery be raising economy, An energy saving important channel.
In numerous residual-heat utilization technologies, Organic Rankine Cycle is since its efficiency is higher, simple in structure, single-machine capacity model 70 DEG C or more of residual heat resources can be widely used in the advantages that standard modular production by enclosing wide, various parts.In recent years, state Inside and outside scholar is to improve Organic Rankine Cycle output power to have carried out a large amount of research work.For the research of Organic Rankine Cycle Mainly by establishing the theoretical analysis method after each component thermodynamical model.But Organic Rankine Cycle actual moving process In influence factor it is more, be typical non-linear relation between output power and each thermodynamic parameter.At present, it tests System output power differs larger with theoretical analysis result, i.e., theory analysis can not test output power to Organic Rankine Cycle Accurately predicted.
BP neural network is also known as error backward propagation method, is a kind of forward direction type network of multilayer.In BP nerves In network, signal is propagated forward, and error is backpropagation.BP neural network has very strong non-linear mapping capability With network structure flexible, it is widely used in the prediction and optimization of energy power system performance.Therefore, foundation has The BP neural network model of machine Rankine cycle, accurately predicts its output power.
Invention content
The purpose of the present invention is to solve existing thermodynamical models to be difficult to Accurate Prediction Organic Rankine Cycle output power Deficiency, propose a kind of Organic Rankine Cycle output power predicting method based on BP neural network.The specific technology of the present invention Scheme includes the following steps:
(1) acquisition of Organic Rankine Cycle operation data
Multigroup test data in organic rankine cycle system operational process is acquired, every group of test data includes following ginseng Number:The volume flow of organic working mediumExpanding machine torque (Torexp), expander inlet pressure (pexp,in), expander outlet Pressure (pexp,out), expander inlet temperature (Texp,in), condensator outlet temperature (Tcon,out), working medium pump discharge pressure (pp,out) and expanding machine output powerAbove-mentioned multigroup test data is grouped at random, be divided into acclimation group data and Test group data;
(2) normalized of gathered data
Due to each parameter the order of magnitude difference it is larger, in order to accelerate the convergence rate of neural network, need to each parameter into Row normalized makes it be converted into the respective value in [0,1] section
In formula, XminFor the minimum value of each parameter, XmaxFor the maximum value of each parameter, X is the gathered data of each parameter,For Each parameter normalization treated numerical value;
(3) foundation of BP neural network
Establish the prediction model of the Organic Rankine Cycle output power based on BP neural network, the neural network prediction model Including an input layer, an intermediate hidden layer and an output layer;Wherein, input layer includes 7 neurons:Organic working medium Volume flow, expanding machine torque, expander inlet pressure, outlet pressure of expansion machine, expander inlet temperature, condensator outlet temperature Degree, working medium pump discharge pressure;Output layer includes a neuron, the i.e. output power of Organic Rankine Cycle;Hidden layer transmits letter Number is tansig, and output layer transmission function is purelin;The neural network prediction model can pass through Calling MATLAB nerve net It realizes in network tool box;The neuron of input layer and output layer is all made of the data after step (2) normalized;
(4) training and test of neural network
Neural network maximum frequency of training and training objective error are set, by the training after normalized in step (2) Data are input in the neural network that step (3) is established and are trained, after the completion of waiting for neural metwork training, test data is defeated Enter to neural network and tests;Wherein, training objective error is evaluated using mean square error:
In formula, Q is input layer set, and Y (k) is neural network prediction value, and t (k) is actual test value, is made It obtains mean square error and is less than training objective error;
(5) in test data neural network output data, that is, expanding machine output power anti-normalization processing
After the completion of being tested neural network according to step (4), neural network output data is subjected to anti-normalization processing:
In formula, YminFor the minimum value of expanding machine output power in all acclimation group data, YmaxAt all domestications The maximum value of expanding machine output power in reason group data,Output valve is tested for neural network, Y is the survey after anti-normalization processing Try output valve;
(6) output power of Organic Rankine Cycle is predicted using the neural network of foundation
The data of previous cycle are re-incorporated INTO step (1) by circulation step (1)-(5), will be passed through at step (2) normalization 7 operating parameters after reason are input in the neural network that step (4) is established, and are obtained after corresponding output valve according still further to step (5) anti-normalization processing is carried out, and then obtains the output power of subsequent cycle prediction;
The beneficial effects of the present invention are:Compared with traditional thermodynamics analysis methods, the nerve net of the invention built Network model can fast and accurately predict Organic Rankine Cycle output power, avoid and ground to the operation mechanism of various parts Study carefully, and working efficiency and precision of prediction can be obviously improved, reliable guide is provided for the optimization of Organic Rankine Cycle.
Description of the drawings
Fig. 1 is the structure chart of BP neural network
Fig. 2 is the prediction result and comparison of test results figure of BP neural network model;
Specific implementation mode
The present invention provides a kind of Organic Rankine Cycle output power predicting method based on BP neural network, with reference to The embodiment of Vehicular internal combustion engine Organic Rankine Cycle residual neat recovering system is next, and the present invention is described in detail.
It is absorbed in evaporator using the exhaust heat of certain diesel engine for automobile as the heat source of Organic Rankine Cycle, organic working medium Become saturation or superheated steam after diesel engine exhaust waste heat, subsequently enter expanding machine and push its acting, the steam exhaust after acting enters Condenser returns to after being condensed into saturated liquid in fluid reservoir, and working medium extraction is sent in evaporator by working medium pump again, hereafter, organic Rankine cycle carries out cycle operation.
(1) acquisition of Organic Rankine Cycle operation data
During being acquired to Organic Rankine Cycle operation data, by the stable conditions of diesel engine in rotating speed 1900rpm, torque 900N.m, output power 180kW.By adjusting organic working medium circular flow and expanding machine torque, acquisition The test data of 2100 groups of organic rankine cycle systems operation, including:The volume flow of organic working mediumExpanding machine torque (Torexp), expander inlet pressure (pexp,in), outlet pressure of expansion machine (pexp,out), expander inlet temperature (Texp,in), it is cold Condenser outlet temperature (Tcon,out), working medium pump discharge pressure (pp,out) and expanding machine output powerCalling MATLAB The randperm functions of R2010a randomly select 2000 groups from 2100 groups of test datas and are used as training sample, remaining 100 groups of examination Data are tested as test sample.
(2) normalized of gathered data
Since the order of magnitude difference of each parameter is larger, in order to accelerate the convergence rate of neural network, by 2100 groups of experiment numbers According to being normalized, it is made to be converted into the respective value in [0,1] section
In formula, XminFor the minimum value of each parameter, XmaxFor the maximum value of each parameter, X is the gathered data of each parameter,For Each parameter normalization treated numerical value.
(3) foundation of BP neural network
The Organic Rankine Cycle output based on BP neural network is established by the newff functions of Calling MATLAB R2010a Power prediction model, the neural network prediction model include an input layer, an intermediate hidden layer and an output layer.Its In, input layer includes 7 neurons:The volume flow of organic working medium, expanding machine torque, expander inlet pressure, expanding machine go out Mouth pressure, expander inlet temperature, condensator outlet temperature, working medium pump discharge pressure.Output layer includes a neuron, that is, is had The output power of machine Rankine cycle;Hidden layer transmission function is tansig, and output layer transmission function is purelin.The nerve net Network prediction model can be realized by Calling MATLAB R2010a Neural Network Toolbox.
(4) training and test of neural network
It is 2000 that neural network maximum frequency of training, which is arranged, and training objective error is 0.001, learning rate 0.3, study Function selects the trainlm of L-M optimization algorithms.Wherein, training objective error is evaluated using mean square error:
In formula, Q is input layer set, and Y (k) is neural network prediction value, and t (k) is real output value.
Training data after normalized in step (2) is input in the neural network that step (3) is established and is carried out Training thinks that neural metwork training is completed when mean square error is less than training objective error 0.001.The results show that by 3 After second, the training of 160 steps, the mean square error of network reaches 0.000486, and training is completed.Then, 100 groups of test datas are input to Neural network is tested.
(5) anti-normalization processing of test data
After the completion of being tested neural network according to step (4), neural network output data is subjected to anti-normalization processing:
In formula, YminFor expanding machine output power in 2000 groups of test datasMinimum value, YmaxFor 2000 groups of examinations Test expanding machine output power in dataMaximum value,Output valve is tested for neural network, Y is after anti-normalization processing Test output valve.
Test output valve after anti-normalization processing is compared with test data, the comparing result meter provided by Fig. 2 It calculates it is found that the maximum relative error of neural network model is 7.7%, related coefficient 0.9934, and most test data Relative error be less than 5%.It follows that neural network model has higher precision of prediction, this neural network can be used In the prediction of Organic Rankine Cycle output power.
(6) output power of Organic Rankine Cycle is predicted using the neural network of foundation
It will be input to the neural network that step (4) is established by 7 operating parameters after step (2) normalized In, it obtains carrying out anti-normalization processing, and then the output power predicted according still further to step (5) after corresponding output valve.

Claims (2)

1. a kind of Organic Rankine Cycle output power predicting method based on BP neural network, which is characterized in that including walking as follows Suddenly:
(1) acquisition of Organic Rankine Cycle operation data
Multigroup test data in organic rankine cycle system operational process is acquired, every group of test data includes following parameter:Have The volume flow of machine working mediumExpanding machine torque (Torexp), expander inlet pressure (pexp,in), outlet pressure of expansion machine (pexp,out), expander inlet temperature (Texp,in), condensator outlet temperature (Tcon,out), working medium pump discharge pressure (pp,out) and Expanding machine output powerAbove-mentioned multigroup test data is grouped at random, is divided into acclimation group data and test group number According to;
(2) normalized of gathered data
Since the order of magnitude difference of each parameter is larger, in order to accelerate the convergence rate of neural network, need to return each parameter One change is handled, it is made to be converted into the respective value in [0,1] section
In formula, XminFor the minimum value of each parameter, XmaxFor the maximum value of each parameter, X is the gathered data of each parameter,For each ginseng Numerical value after number normalized;
(3) foundation of BP neural network
The prediction model of the Organic Rankine Cycle output power based on BP neural network is established, which includes One input layer, an intermediate hidden layer and an output layer;Wherein, input layer includes 7 neurons:The volume of organic working medium Flow, expanding machine torque, expander inlet pressure, outlet pressure of expansion machine, expander inlet temperature, condensator outlet temperature, Working medium pump discharge pressure;Output layer includes a neuron, the i.e. output power of Organic Rankine Cycle;Hidden layer transmission function is Tansig, output layer transmission function are purelin;The neural network prediction model can pass through Calling MATLAB neural network work Have case to realize;The neuron of input layer and output layer is all made of the data after step (2) normalized;
(4) training and test of neural network
Neural network maximum frequency of training and training objective error are set, by the training data after normalized in step (2) It is input in the neural network that step (3) is established and is trained, after the completion of waiting for neural metwork training, test data is input to Neural network is tested;Wherein, training objective error is evaluated using mean square error:
In formula, Q is input layer set, and Y (k) is neural network prediction value, and t (k) is real output value so that Square error is less than training objective error;
(5) in test data neural network output data, that is, expanding machine output power anti-normalization processing
After the completion of being tested neural network according to step (4), neural network output data is subjected to anti-normalization processing:
In formula, YminFor the minimum value of expanding machine output power in all acclimation group data, YmaxFor all acclimation groups The maximum value of expanding machine output power in data,Output valve is tested for neural network, Y is that the test after anti-normalization processing is defeated Go out value.
2. a kind of Organic Rankine Cycle output power predicting method based on BP neural network described in accordance with the claim 1, It is characterized in that, circulation step (1)-(5), the data of previous cycle is re-incorporated INTO step (1), step (2) will be passed through and normalized Treated, and 7 operating parameters are input in the neural network that step (4) is established, and are obtained after corresponding output valve according still further to step (5) anti-normalization processing is carried out, and then obtains the output power of subsequent cycle prediction.
CN201810361923.8A 2018-04-20 2018-04-20 Organic Rankine Cycle output power predicting method based on BP neural network Pending CN108564172A (en)

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CN110263990A (en) * 2019-06-10 2019-09-20 山东大学 Vortex compounding machine flow torque prediction method and system neural network based
CN113255211A (en) * 2021-05-14 2021-08-13 湘潭大学 BP neural network and multi-objective optimization based organic Rankine cycle working medium screening method
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CN109190327A (en) * 2018-11-23 2019-01-11 华北电力大学(保定) Organic Rankine Cycle system analysis optimization method, device and equipment
CN109190327B (en) * 2018-11-23 2022-11-22 华北电力大学(保定) Method, device and equipment for analyzing and optimizing organic Rankine cycle system
CN110263990A (en) * 2019-06-10 2019-09-20 山东大学 Vortex compounding machine flow torque prediction method and system neural network based
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