Cylinder-to-cylinder and cycle-to-cycle variation in combustion process in radial aircraft engine

Michał Gęca

doi:10.19206/ce-2017-113

Abstract

Cycle-to-cycle variation in combustion in a single cylinder of a radial engine has an impact on that in others and the entire engine. Steady- and transient-state engine operation was investigated, and the transient states were generated by cyclic changes in the timing of fuel injection to a given cylinder, having others operated on the same mixture composition. The measurement of pressure in the combustion chamber allowed for specifying indicated mean effective pressure (IMEP) in all cycles. The time series of IMEP were studied with mathematical techniques of non-linear dynamics, i.e. a wavelet transform and a multifractal analysis. Controlled disturbances in mixture composition in a single cylinder can have an impact on certain cylinders only. Cylinders 3, 5, 7 and 9 are most responsive to such disturbances, which proves their least cycle-to-cycle variation in combustion.

Highlights

Cycle-to-cycle variations in cylinder operation is typical of multi-cylinder engines
Combustion process was monitored with OPTRAND M 3.5 x 0.6 optoelectronic sensors installed in special adapters screwed in the central section of the head
A wavelet power spectrum (WPS) of the time series of indicated mean effective pressure (IMEP) is defined as the square of the absolute value of Continuous Wavelet Transform (CWT)

Summary

Introduction

Cycle-to-cycle variations in cylinder operation is typical of multi-cylinder engines. Cycle-to-cycle variation in the multi-cylinder engine can result from irregularly distributed any of the above factors in cylinders [15] as well as non-linear entire combustion (several possible courses of this process). The author proposed [4] a physically proven non-linear map as a model of cylinder-to-cylinder variation in the SI engine He discussed an approach of symbol rates statistics to digitize model and research time series. The methods to investigate time series of cylinder pressure with non-linear dynamics are efficient and allow for an in-depth understanding of an internal combustion engine. There are applied quantitative methods as a multifractal analysis and qualitative methods as a wavelet transform These two approaches allowed for investigating an operating cycle in each cylinder and the impact of combustion in a given cyclinder on combustion in others. To monitor the parameters of its performance, the research engine is equipped with sensors such as 4 pressure transmitters MPX4250 under the carburetor, 2 pressure transducers MPX4250 Motorola in each of the intake pipes at the compressor and head

Research object and the engine test stand

Research methodology

Research results

Findings

Summary