Measuring method for diesel multihole injection nozzles

doi:10.1016/S0924-4247(03)00205-X

Sensors and Actuators A: Physical

Volume 107, Issue 2, 15 October 2003, Pages 152-158

https://doi.org/10.1016/S0924-4247(03)00205-X Get rights and content

Abstract

A vast majority of the medium and high speed diesel engines are equipped with multihole injection nozzles nowadays. Inaccuracies in workmanship and changing hydraulic conditions in the nozzles result in differences in injection rates between individual injection nozzle holes. The new deformational measuring method described in the paper allows injection rate measurement in each injection nozzle hole. The differences in injection rates lead to uneven thermal loads of diesel engine combustion chambers.

The criterion of the injected fuel is expressed by the deformation of membrane occurring due to the rapid rise of the fuel in the measuring space and the collision of the pressure wave against the membrane. The pressure wave is generated by the injection of the fuel into the measuring space. The pressure wave is analysed by the theory of hydraulic impact in the high-pressure pipes. The membrane deformation is measured using strain gauges, glued to the membrane and forming the Wheatstone bridge. We devoted special attention to the temperature compensation of the Wheatstone bridge and the membrane, heated up during the measurements. All four strain gauges were arranged in a full Wheatstone bridge configuration and glued to the membrane. The strain gauges are all exposed to identical temperature resulting in a temperature compensated Wheatstone bridge.

Described in the paper are the measurements of a three-hole nozzle and the reasons analysed of injection rate differences in the injection nozzle holes. We divided the causes of the inequality in the injection rate into structural and hydraulic groups.

Introduction

Any further thermodynamic optimisation of the diesel engine can only be carried on by an ever more accurate knowledge of parameters that will exert influence upon fuel combustion in the engine. The process of fuel injection in diesel engines has a great impact on combustion. Knowing the injection rate, is thus crucial in understanding the combustion in the engine.

Measuring of the injection rate is carried out on test benches for testing injection systems according to different measuring methods. With Zeuch’s measuring method, the criterion for the injection rate is the alteration of the piston stroke due to the force exerted by the fuel injection jet [1]. With the charge measuring method the criterion for the injection rate is the charge created by the friction of the fuel in the nozzle, friction of the jet against the surface of the sensor, and by the Seebeck effect [2]. However, the most frequently applied method of measuring the injection rate nowadays is the Bosch measuring method [3]. Analysis of injection rate measurements was done by many authors [4], [5], [6]. The Bosch and Zeuch injection rate measurement methods were compared by Bower and Foster [7]. They used a high-pressure accumulator-type injection system and a single-hole nozzle injection fuel at high frequencies and quantities (45–100 mm³ per injection). The flat injection rate pattern of the accumulator injection system has allowed convenient comparison of the steady flow measurement capability of the two methods. They also compared Bosch and Zeuch injection rate measurement methods for rotary pump speeds of 1000–2000 rpm and loads of about 50 mm³ per injection.

All the measuring methods give accurate results of the injection rate in single-hole nozzles. With multihole nozzles, however, they tell us nothing about possible differences in injection rates between individual holes of the nozzle. In order to find out the differences in injection rates between individual holes of the injection nozzle, we have developed a deformational measuring method described in detail in this paper. With multihole nozzles, the deformational measuring method facilitates measurement of the injection rate at each hole of the nozzle.

After the completed endurance test of the engine, we noticed different traces of temperature loads in the wall of the combustion chamber (ω combustion process) at the spots of the contact jet–piston chamber wall, which indicates differences in injection rates between individual holes of the nozzle. The measurements of the injection rates presented in the article confirm our suppositions.

Section snippets

Deformational measuring method

Fig. 1 depicts the deformational measuring method. The criterion of the injected fuel is expressed by the deformation of membrane occurring due to the collision of the pressure wave against the membrane. The pressure wave is generated by the injection of the fuel into the measuring space. For the duration of measurements, the measuring space must be filled with fuel to maintain an overpressure of 5 kPa. For each hole of the nozzle, the measuring device must have a measuring space of its own into

Measuring the injection rate

Injection rates were measured at three-hole nozzles (Fig. 6). A measuring device designed for this type of nozzle is shown in Fig. 1. To this end, a conventional injection system of pump—high-pressure pipe–injection nozzle was utilised. We measured pressure p_II at the inlet of the nozzle, as well as the needle lift h_i and the injection rate at each hole of the nozzle. The measurements of the injection nozzle were performed by means of the Friedmann and Maier test stand for testing injection

Summary

The article deals with deformational measuring method that facilitates measurement of injection rates at each hole of the multihole injection nozzles. The criterion of the injected fuel is expressed by the deformation of membrane occurring due to the rapid rise of the fuel in the measuring space and the collision of the pressure wave against the membrane. The pressure wave is generated by the injection of the fuel into the measuring space. For each hole of the nozzle the measuring device must

Milan Marčič received his MS degree in 1977 and PhD degree in 1988 from University of Ljubljana. He joined TAM (factory of truck and engines) in 1978 where he was involved in combustion and fuel injection processes. He subsequently joined University of Maribor where he has been professor of thermodynamics and experimental methods since 1992.

References (11)

W. Zeuch, Neue Verfahren zur Messung des Einspritzgesetzes und Einspritz-Regelmässigkeit von Diesel-Einspritzpumpen,...
M. Marčič
New diesel injection nozzle flow measuring device
Rev. Sci. Instrum.
(2000)
W. Bosch, The fuel rate indicator: a new measuring instrument for display of the characteristics of individual...
S. Matsuoka, K. Wokota, T. Kamimoto, The measurement of injection rate, in: Proceedings of the IMechE Symposium on...
A. Takamura, S. Fukushima, Y. Omori, Development of a new measurement tool for fuel injection rate in diesel engines,...

There are more references available in the full text version of this article.

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