  Thanks to modern understanding of stellar evolution, we can accurately
measure the age of Open Clusters (OCs). Given their position, they are ideal
tracers of the Galactic disc. Gaia data release 2, besides providing precise
parallaxes, led to the detection of many new clusters, opening a new era for
the study of the Galactic disc. However, detailed information on the chemical
abundance for OCs is necessary to accurately date them and to efficiently use
them to probe the evolution of the disc.Mapping and exploring the Milky Way
structure %to combine accurate chemical information of OCs is the main aim of
the Stellar Population Astrophysics (SPA) project. Part of this work involves
the use of OCs and the derivation of their precise and accurate chemical
composition.We analyze here a sample of OCs located within about 2 kpc from the
Sun, with ages from about 50 Myr to a few Gyr.We used HARPS-N at the Telescopio
Nazionale Gaileo and collected very high-resolution spectra (R = 115\,000) of
40 red giant/red clump stars in 18 OCs (16 never or scarcely studied plus two
comparison clusters). We measured their radial velocities and derived the
stellar parameters.We discussed the relationship between metallicity and
Galactocentric distance, adding literature data to our results to enlarge the
sample and taking also age into account. We compared the result of
observational data with that from chemo-dynamical models. These models
generally reproduce the metallicity gradient well. However, at young ages we
found a large dispersion in metallicity, not reproduced by models. Several
possible explanations are explored, including uncertainties in the derived
metallicity. We confirm the difficulties in determining parameters for young
stars (age < 200 Myr), due to a combination of intrinsic factors which
atmospheric models can not easily reproduce and which affect the parameters
uncertainty
