**5.2 Effects of fuel properties on deposit accumulation**

Deposit accumulation processes were investigated by using the wick combustion burner. Deposit accumulation rate was estimated from the mass of deposit which accumulated on wick and the fuel consumption, and components of the deposit were estimated from the TG-DTA analysis. The main results are summarized as follows:


**1. Introduction**

on this field.

**2. Data reduction**

In the last ten years, the number of natural gas (NG) vehicles worldwide has rapidly grown with the biggest contribution coming from the Asia-Pacific and Latin America regions (IANGV, 2011). As natural gas is the cleanest fossil fuel, the exhaust emissions from natural gas spark ignition vehicles are lower than those of gasoline-powered vehicles. Moreover, natural gas is less affected by price fluctuations and its reserves are more evenly widespread over the globe than oil. In order to increase the efficiency of natural gas engines and to stimulate hydrogen technology and market, hydrogen can be added to natural gas, obtaining

*Dept. of Aerospace and Mechanical Engineering - Seconda Universitá degli Studi di Napoli* 

**A Review of Hydrogen-Natural Gas Blend** 

**Fuels in Internal Combustion Engines** 

Antonio Mariani, Biagio Morrone and Andrea Unich

This chapter gives an overview of the use of HCNG fuels in internal combustion engines. The chemical and physical properties of hydrogen and natural gas relevant for use in internal combustion engines are described. Then a survey on the impact of hydrogen on natural gas engine performance and emissions is presented with reference to research activities performed

In this section the main physical quantities used in this chapter are presented and discussed. The stoichiometric air-fuel ratio on mass basis (AFR*stoich*), defined in equation 1, is the mass of air needed to fully oxidize 1 kg of fuel, while AFR is the ratio between air and fuel mass flow rates, equation 2. The ratio between the actual AFR and the AFR*stoich*, is the relative air-fuel ratio, equation 3. If *λ >* 1 the mixture is *lean* and the oxidation takes place with excess of air respect to the stoichiometric amount; for *λ* values lower than 1 the mixture is *rich*, and the fuel oxidation is not complete. The ratio 1/*λ* is defined as the equivalence ratio *φ*, equation 4.

> *ma mf*

*AFR* <sup>=</sup> *ma mf*

*<sup>λ</sup>* <sup>=</sup> *AFR AFRstoich*

*stoich*

(1)

**2**

*Italy* 

(2)

(3)

*AFRstoich* =

Hydrogen - Natural Gas blends, usually named as HCNG.
