Abstract
A mathematical model of joint operation of a piston engine with pulse turbine drive, compressor as well as air supply of a diesel locomotive is presented in the article. This model in an integral part of the complex engine-generator power unit of a diesel locomotive in steady states and transient conditions, developed by the authors. The periodic process in the exhaust manifold is represented as two specific characteristic ranges which encompass the process of forced exhaust and the scavenging process. The scavenging calculation is carried out jointly with the processes taking place in the inlet manifold of the engine, including inlet devices of the locomotive. The process of forced exhaust is calculated separately from the inlet processes and doesn`t require usage of empirical coefficients of impulsiveness. Both processes are represented as systems of nonlinear algebraic equations describe in the quasi-steady flow of working fluid in the elements of the inlet and exhaust tracts. The gas-dynamic calculation of the turbine in the transition process is conducted while taking into account changes in flow angles on the rotor blades. As a result of numerical calculation of the a8S22W diesel operational indices in transient modes, a satisfactory compliance of the calculated and the experimental results was obtained.
Highlights
The analysis of the operating modes of the diesel engine shows that the engine runs on transient mode for a considerable part of the operation time.The transient modes, accompanying acceleration of the engine, are characterized by sharp increasing of fuel supply into the cylinder of engine and as a result by a reduction of the air excess coefficient λ, reduction of indicated efficiency ηi, significant peak temperature increase of exhaust gases Tt, incomplete combustion of fuel and other negative effects
Experimental studies of an operation of the diesel generator with pulse supercharging when momentary changes of load showed that the ratio of pressure in the inlet manifold Ps to pressure in front of the turbine Pt, is practically always larger than one throughout in the whole period of transient process
The advantages of the pulse supercharging system are a better use of exhaust gases energy, which facilitates the increase in the torque of the turbine and improving the air supply of the diesel engine in the transient processes
Summary
The analysis of the operating modes of the diesel engine shows that the engine runs on transient mode for a considerable part of the operation time.The transient modes, accompanying acceleration of the engine, are characterized by sharp increasing of fuel supply into the cylinder of engine and as a result by a reduction of the air excess coefficient λ, reduction of indicated efficiency ηi, significant peak temperature increase of exhaust gases Tt, incomplete combustion of fuel and other negative effects. In [5, 9, 10, 25, 33], the authors described some interesting simulation models of diesel engine operation in steady conditions and transient states while using 1D models for turbocharger and chosen processes of diesel engines, and in publications [11, 17, 34] 3D CFD models In these works, the research (modelling) object is, among others, a pulse-charged turbine in application for mainly automotive engines. The authors proposed a different approach to modelling of diesel engine exhaust system with pulse turbine supply which does not require implementation of differential equations for calculation of gas exchange, using experimental pulse indices or creation of complex, 1D or 3D models, e.g. for the piston part of the traction diesel engine, turbocharger
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