Influence of Innovative Woodchipper Speed Control Systems on Exhaust Gas Emissions and Fuel Consumption in Urban Areas

Abstract

This paper discusses the determination of fuel consumption and exhaust gas emissions when shredding branches in urban areas. It aimed to determine the hourly emission of exhaust gases to the atmosphere during such work and to identify the designs that can reduce it. The research was carried out with a cylinder woodchipper driven by a low-power (9.5 kW) combustion engine. There were three configurations of the tested drive unit: The factory setting (A) with a carburettor fuel supply system, modernized by us to include an electronic injection system (B). This system (B) was expanded with an adaptation system patented by the authors (P. 423369), thus creating the third configuration (C). The research was carried out when shredding cherry plum (Prunus cerasifera Ehrh. Beitr. Naturk. 4:17. 1789 (Gartenkalender 4:189-204. 1784)) branches with a diameter of 80 mm, which presented a large load for the machine. The machine was operated by one experienced operator. The average operating conditions during the tests were as follows: Branch delivery frequency of about 4 min−1 and mass flow rate of about 0.72 t h−1. During the tests with the use of PEMS (portable emissions measurement system, here Axion RS from Global MRV), we analyzed the emissions of compounds, such as CO, CO2, HC, and NOx, and determined the fuel consumption based on the carbon balance. The research showed that the use of an injection system (B) reduced fuel consumption from 1.38 to 1.29 l h−1 (by 6.7%) when compared to the carburettor system (A). Modernization of the injection system (B) with an adaptive system (C) reduced fuel consumption from 1.38 to 0.91 l h−1 (by 34%) when compared to the carburettor system (A). An hour of shredding with a cylinder chopper emits the following amounts of flue gases: design A (HC 0.013 kg h−1; CO 0.24 kg h−1; CO2 2.91 kg h−1; NOx 0.0036 kg h−1), design B (HC 0.0061 kg h−1; CO 0.20 kg h−1; CO2 2.77 kg h−1; NOx 0.0038 kg h−1), and design C (HC 0.017 kg h−1; CO 0.22 kg h−1; CO2 1.79 kg h−1; NOx 0.0030 kg h−1). The adaptive system entails significant reductions in non-HC emissions, which indicates that the system needs to be improved with respect to fuel-air mixture control for its enrichment of the low-to-high-speed change. The admissible emission limits for harmful compounds in exhaust gas for the tested group of propulsion units are in accordance with the provisions in force in the European Union from 2019 for the tested propulsion units during operation, with a full CO load about 6100 g h−1 and HC + NOx about 80 g h−1. The tested propulsion units emitted significantly less pollution under real operating conditions (because they did not work under full load throughout the entire test sample).